Pressure operated electric switch



Patented Aug. 5, 1941 PRESSURE OPERATED ELECTRIC SWITCH Sydney Clifford Wayman, Darthill, March, England Application November 2, 1939, Serial No. 302,530 In Great Britain November 11, 1938 (C1. ZOO-82) 1 Claim.

This invention relates to a switching device for use in connection with internal combustion engines, especially upon automobiles, and arranged to be operated by the supply of lubricating oil to the internal combustion engine.

Switches of the type referred to have already been proposed but suffer from serious objections in that they depend for operation upon the oil pressure obtaining in the lubricating system of the internal combustion engine. It is thus necessary to arrange that the switch shall not be operated until a certain minimum pressure is developed in the lubricating system and this minimum pressure is invariably such that it cannot easily be developed when starting the engine by hand and results in a considerable drain on the battery when the engine is started by means of the starter motor. With such devices it is therefore the practice to provide a control whereby the device can be rendered inoperative when starting the engine.

Furthermore, since such devices break the electric circuit controlled by the switch, which of course includes the ignition circuit, when the pressure in the lubricating system falls below the predetermined minimum in the event of a bearing being run with consequent fall in the oil pressure to zero the engine stops and can only be driven by operating the control referred to above or by otherwise rendering the switching device inoperative. This is of course liable to be very inconvenient since it is obviously necessary when a bearing is run to continue driving until a garage is reached where the necessary repairs can be effected.

According to the present invention there is provided a device embodying an electrical switch and intended to be inserted between an internal combustion engine and the pump supplying lubricating oil thereto, said device comprising a chamber adapted to be connected to said pump or a conduit extending therefrom and having an outlet for completing the oil circulating system, a member normally closing said outlet and displaceable to open the same by oil pressure within the chamber, said electric switch being controlled by said member and arranged to be closed just before said outlet is opened.

This result accrues from the fact that, in order to close the switch, it is only necessary to build up within the chamber referred to sulflcient pressure to cause a slight movement of the member normally closing the outlet from which oil is subsequently supplied to the engine; thus it is V unnecessary to build up a working pressure in the whole lubricating system of the engine to close the switch as is the case in the devices previously proposed. Furthermore, it will be apparent that should the pressure on the engine side of the device fail, e. g. by reason of a damaged bearing, the switch is not opened since the member which operates the switch will only move enough to close partially the outlet which completes the oil circulating system Whereas it must move beyond this position for the switch to be opened. On the other hand, should the oil supply fail by reason of a broken pump or pipe leading from the pump to the device or by reason of lack of oil, the switch is operated immediately and the engine cannot be restarted until a sufficient supply of lubricant is ensured.

In order that this invention may be clearly understood and readily carried into efiect I have appended herewith a sheet of drawings illustratin an embodiment thereof, and wherein:

Fig. 1 is a sectional elevation.

Fig. 2 is an outside elevation, and

Fig. 3 a section on the line 3a of Fig. 1.

Referring to the drawing the device shown is adapted to be connected in the oil circulating system of an internal combustion engine, for which purpose an inlet union l is suitably threaded for connection to the outlet of an oil pump or a conduit extending from such outlet. The oil circulating system is completed through ports 2 in the wall of a cylinder 3 preferably formed in tegral with the union I. These ports communicate with a collar or housing 4 having an outlet union 5 adapted to have connected to it an oil circulating pipe. When the engine is stopped the ports 2 are closed by a plunger 6 slidable in the cylinder 3, such plunger being held in the closed position by a coiled compression spring 6a disposed about a rod 1 carrying the plunger at one end.

This coiled compression spring is interposed between the plunger 6 and an annular abutment 8 surrounding an aperture at one end of an integral tubular extension 9 of the cylinder 3. A nut Ill combined with a lock nut H are threaded on an extension I2 of the rod 1 to form an abutment against the adjacent end of the tubular extension 9, in order to limit the closing movement of the plunger 6.

Disposed about the threaded stem I2 is conducting ring 13 insulated from the stem l2 by a collar l4. Rings l5 can be threaded on the stem l2 to afford a means for adjusting the position of the contact I3 on the stem l2, insulating rings I8 being interposed between the rings I5 and the contact i 3.

When the plunger 6 is urged axially along the cylinder 3 by the pressure of oil entering the union 1, the ports 2 are uncovered and the normal oil circulation is established. During this movement, in advance of actual opening of the ports 2, the contact l3 engages the free ends of a pair of resilient contact strips ii and I8. These contact strips IT and I8 are supported by terminals [1a and I to respectively to which suitable loads are connected with the ignition circuit of the engine. This connection is preferably on the low tension side of the circuit so as to avoid high tension sparking at the contacts. These contacts are enclosed in a housing I 9 detachably threaded or otherwise secured to a cap 20 supporting within it the part 9 of the cylinder 3. The contacts can be individually adjustable along their terminals or the terminals can be translatively adjustable. It will be understood that the contacts i'! and I 8 are insulated from the member 9.

The free ends of the contacts [7 and it are bent inwardly as at Ill) and It?) to enable the periphery of the contact [3 to slide against such free ends with little friction.

The casing Hi can be in the position shown in Fig. 1 in which the connection to the oil circuit is above the casing, and the oil accumulating in the casing l3 can surround the contacts. Surplus oil can escape back to the engine sump or other suitable part by a suitable union 2!. However, if desired the device may be reversed so that the oil inlet is lowermost.

It will be apparent that when the engine has stopped the drop in oil pressure will enable the spring 6 to reassert itself to move the plunger 5 to the closed position, whereupon all electrical circuits controlled by the switch will be broken.

When the invention i applied to a motor road vehicle and terminals 11a and I8a may be connected between the battery and all of the electrical devices of the vehicle, other than the starter motor and the side and tail lamps.

I claim:

A fluid-operated electric switch comprising a body portion providing therein, in axial alignment a cylinder having an inlet at one end, a chamber at its other end of reduced diameter and an opening of further reduced diameter at the far end of said chamber, said chamber providing an internal shoulder at its end next said opening; a plunger in said cylinder having a sliding fit therewith; a plunger rod projecting axially from said plunger into and through said chamber and of less diameter than said chamber and of the same diameter as and projecting through said opening at the far end of said chamber; a compression spring within said chamber and on said rod, said spring having one end bearing against said shoulder and its other end bearing against said plunger; screw threads on the end portion of said rod exterior of said opening; an adjustable stop on said screw-threaded end portion of the rod adjacent said opening for engagement with the said body portion to limit inward movement of the rod under influence of the spring; a contact member also carried by said threaded end of the rod beyond said stop and adjustable independently of adjustment of said stop; and a pair of cooperating resilient contact strips engageable by said contact member upon sliding the plunger and rod against action 01" the spring and under influence of fluid pressure on the plunger at the inlet end of the cylinder.

SYDNEY CLIFFORD WAYMAN. 

